Back to bits and bytes, consider iOS having no notion of a cursor, or the Mac not having a touch-screen, or a stylus, to name but a few transaltion challenges.

a través de ARM Mac: Piece of Cake Or Gas Refinery? – Monday Note

…The move isn’t universally praised, to the contrary.

For perspective, 2007 iPhone shipments are not impressive: $367M in (calendar) 2007, less than 1.4% of Apple’s total $26.5B.
Compared to modest first-year iPhone sales, spending $278M to acquire Palo Alto Semiconductor looks out of proportion. And, of course, let’s not forget a context where Intel reigns supreme having just “captured” the Mac. As always, references to Apple’s “well-known” arrogance are at the ready: Who do these guys think they are, what do they know about microprocessor design and manufacturing?

Answers start to come out in 2010, with the A4 processor powering the first iPad and the iPhone 4. The first Apple-designed processors are deemed serviceable, a reluctant compliment. The 2011 A5 and 2012 A6 follow without drama. But, in 2013 Apple surprises everyone with an industry-first, a 64-bit mobile processor, the A7 — for the iPhone 5S.
At the time, as I recount in a snarky Monday Note titled 64 bits. It’s Nothing. You Don’t Need It. And We’ll Have It In 6 Months, semiconductor “industry observers” pretend to be unimpressed, calling Apple’s 64-bit processor mere markitecture. The pooh-poohing doesn’t resist the first serious benchmarks measuring how ahead of the pack the A7 is. Then, the “desktop-class” phrase appears following a comparison with entry-level x86 processors:

Right away, speculation starts: Apple will soon kick x86 processors out of the Mac line and replace it with its own processors. For the next five years, nothing of the sort happens. Instead, Apple follows up with one interesting home-grown chip after the other: iPhone A8, 9, 10 and A11 processors, S chips for the Watch, W processors for the company’s earphones and T chips for Mac Secure Enclaves.

Thinking of future Macs would be simpler if its putative new processors weren’t iOS-compatible, but here we are. That being said, setting aside inopportune claims of courage, Apple is a cautious company, well aware of the risks in trading a relatively simple life of separate Mac and iOS product lines for a complicated hybrid platform. This coming transition will be interesting to watch.